miller



3 Sheets-Sheet l \XX\ INVENTOR DONALD F MILLER D. F. MILLER CHAIN LINK Feb. 9, 1960 original Filed March 24, 1952 D. F. MILLER CHAIN LINK Feb. 9, 1960 5 Sheets-Sheet 2 Original Filed March 24, 1952 INVENTOR DONALD F M/LLER BYZMM, 73M

IIIIHI-IIIIIIIIII ATTORNEY Feb. 9, 1960 v D. F. MILLER 2,923,999

CHAIN LINK Original Filed March 24, 1952 jfl' .9

3 Sheets-Sheet 3 MEQ.. I3

Kif m n rr '3 4 ---B INVENTOR 22 DONLDE MILLER gwn/mmm ATTORNEY United States Patent CHAIN LINK Donald Floyd Miller, Pompton Lakes, NJ., assgnor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Original application March 24, 1952, Serial No. 278,252,

now Patent No. 2,755,533, dated July 24, 1956. Digsdard this application January 16, 1956, Serial No.

7 Claims. (Cl. 26--61) This invention relates to an apparatus for stretching webs and more particularly webs of sheet materials. Still more particularly it relates to an apparatus for simultaneously stretching webs in a lateral and longitudinal direction.

An object of this invention is to provide an improved apparatus for stretching webs. A further object is to produce such apparatus which is simple in construction and effective in operation. A still further object is to provide such apparatus wherein the degree of lateral and longitudinal stretching can be regulated in a simple manner. Still other objects will be apparent from the following specification.

The apparatus of this invention will now be described with reference to the accompanying drawings which form a part of this specification. In the drawings which illustrate practical embodiments of the invention,

Fig. 1 is a top plan view of a stretching apparatus embodying the invention,

Fig. 2 is a perspective view in a larger scale of a portion of the adjustable stretching unit showing the cam track, chain links and a gripper,

Fig. 3 is a section taken along the line 3 3 of Fig. 2. showing the chain links, gripper and web,

Fig. 4 is a perspective view of a link structure,

Fig. 5 is a perspective view of an alternative link structure,

Fig. 6 is a plan view of a chain with four links in stacked relationship,

Fig. 7 is a section of the upper part of a chain with four links in stacked relationship,

Fig. 8 is an elevation of a part of a chain with three links in stacked relationship,

Fig. 9 is a plan view of a chain link with `a curved slot in closed position,

Fig. 10 is a plan view of a chain link with a curved slot in an extended position,

Fig. 11 is a schematic view of two links with the cam surface opposite from the direction of travel,

Fig. 12 is a schematic view of two links with the cam surface in the same direction of travel,

Fig. 13 is a plan view of a series of grippers mounted on chain pins, and

Fig. 14 is a sectional view taken along the line B-B of Fig. 13.

Referring now to Fig. 1, bedplates 1 and 2 are pivotally mounted on a suitable frame 3 shown in dotted outline by means of pivot pin 4 which interfits with a hole 5 on the lateral lug extension 6 of bedplate 2. The pin is xed to lug extension 7 on bedplate 1. The bedplates rest on the frame member and their position with respect to each other and axis A-A can be regulated by means of lead screw 8 that is journaled in bearing 9 which is pivotally mounted on plate 2 and is threadably engaged with the upstanding lug 10 which is similarly pivotally mounted on bedplate 1. Screw 8 is fastened suitably at its journaled end so that it will turn freely but cannot move along its axis. The other end of the screw is provided with a handle 11 so that it can be turned. When the handle is'turned in one direction the bedplates are drawn closer together and when turned in the opposite direction spread farther apart. This adjustment determines the degree of lateral stretching given to web W (a transparentnon-oriented polymer).

While the bedplates are 'shown as being pivoted on a common pin this construction, while simple and practical, is not essential as the plates can be pivoted separately or provided with lead screws and threaded lugs so that each end can be adjusted and admit of the stretching ofv wider webs. Various modifications can be made to permit angular displacement of the plates from a common axis.

The degree of longitudinal stretching is determined by the variable pitch stretcher chains 12. They are identical in construction although reversed in direction. The stretcher chains consist of a series of identical links. Each link consists of a at L-shaped link body member 14 which is provided with a pivot hole 15, which, as shown in Figs. 2 and 4 consists of a round hole. Spaced from this hole is an elongated slot 16 that can be straight or curved. The tip 17 of the link coacts with a cam track and this is explained further below. The lower end of the slot preferably is half-round and its center preferably is in the same longitudinal axis as an extension of the diameter passingthrough the center axis of the pivot hole. direction as illustrated in Figs. 1l and 12.

In the link of Figs. 4, the axis of the slot is at an angle greater than from said longitudinal axis. This angle determines the force F tending to rotate the link around its axis. The pitch of the chain and the degree of longitudinal stretching can be varied in the case of the specific shape of link of Fig. 4 from x to nx. In the link of Fig. 4 pivot hole 15 is in the outer, upper part of the toe and the slot 16 extends along the base of the L-shaped link. The side and top of this link form a contacting surface to engage with a cam track which regulates the rate and extent of their pivoting and the consequent distance between the centers of the adjacent pins. This, in turn, regulates the rate and extent of longitudinal stretching of the web.

Variable pitch chain 12 as shown in Fig. 2 is made by joining two sets of alternate pairs of links by means of pins 18 which pass through the pivot hole 15 of one link and the elongated slot 16 of the next link in the chain. These links are stacked alternately above and below each other as shown in Figs. 1 and 2 to form a closed chain. Two sets of links are shown in these gures and they are spaced a short distance apart by intervening guide members. Thus, as shown in Fig. 2 they are separated by guide plate 35. The round surfaces of pins 18 between the two sets mesh with a driving sprocket 19 and idler sprocket 20. The teeth on the driving sprocket are spaced to have a pitch equal to distance nx so that it will mesh with the pins when the links are at their maximum extended position. The teeth on the idler sprocket are so spaced that the pitch is equal to distance x. This means that the links are at closed position as they enter stretching units 13.

The path of pins 18 between idler sprocket 20 and the guide roller 21 is essentially a straight line. The closed chain 12 passes around driving sprocket 19 which is spaced above and to one side of guide roller 21 and returns to idler sprocket 20 forming a triangular shaped path. The sprockets and roller may be journaled on stub shafts suitably mounted on the bedplates. The links in the chain on bedplate 1 are reversed with respect to those on bedplate 2.

The upper end of each pin or alternate pins or regularly spaced pins is extended as shown in Figs. 2 and 3' Patented Feb. 9, 1960 The chains can be operated in either l 3 bracket. forked and has an open-.ended slot26 which engages with adjacent chain pin 18. This structure keeps the grippers in proper alignment during the stretching operation. The pivot pin V`may be fixed to the bracket on opposite sides of the gripper arm or fixed to the gripper arm Aand journaled in the bracket on each side of the slot. The chain pin also extends through'a gripper base P1ate'27 which extends below the projection of the bracket and vunder the gripper arm. This plate serves as a rest for the Aselvage of web W. It may be integral with the bracket body 22 or welded or otherwise affixed thereto, e.g., by means of pins 28. This form` of gripper is common in tenter frames. When tension is applied to stretch the web, the gripper arm pivots to grip the web more tightly. Only one gripper is shown in Fig. 2 for the sake of clarity. They may be disposed on each pin 18 as shown in Figs. 13 and 14.

Bedplates 1 and 2 are provided with guide rails 2. They may be cast integrallywith the bedplates or may be welded, bolted or otherwise aixed to the latter. The inside surface of the rails is substantially parallel tothe locus of the pins as they pass from the idler sprocket 20 to the guide roller 21. Second guiding; rails are also mounted on the bedplates. vThey are pivoted at their respective lower end on pivot pin 31. The opposite ends ofthe guide rails have the end of a screw 32 attached thereto. Each screw is threadably engaged with an upstanding lug 33 on the respective bedplate. The outer end of the screws are provided with turning handle 34. As shown the guide rail 30 is in the Vform of a Ufshaped channel. A centralplate 35 extends from each channel, its upper and lower surfaces act as bearing surfacesfor the iiat portion of the inner links. The outer edge of each central plate is disposed parallel with the inner edge of guiderail 29 when in innermost position and the distance between these edges when in such yposition is slightly greater than the diameter of pins 18. `The inner edge of the U-shaped channel slants with respect to theA edges of the guide rail and forms a slanting cam track 36 which engages with the edge and end of each L-shaped link. By adjusting the U-shaped channels by means of screws 32 one can regulate the distance between each two adjacent pins as one of the pins of each pair slides in elongated slots 16. The degree of slant of the rU- shapedguide Vrail can be regulated so that the amount of longitudinal stretch of the web can be varied from .x to nx. -In general, the degree is adjusted so thatthe distance does not increase to the full amount nx.

Tripper arms y37 are placed in the pathof the vgripper arms ator near theend of `guiderails 29 to ldisengagethe grippers. Apart ,of the tripper arm is also shown infig. 2 and this part forms a cam surface whichlifts each gripper arm and removes it from contact with the web-,as the chain moves past the gripper release station.

As the links pass from the cam track due to tension on the chains and the fact that the teeth of driving sprocket 19 are spaced at maximumpitch thepins18 extend apart to their permitted maximum distance.

Link-realigning unit-38 isfplaced inthe path of the pins between the drivingand drivensprockets and preferably near the latter in order to assist in bringing thel links Vinto alignment before they pass intothe stretching unit or zone. These units may have a construction similar to units 13 and be composed yof, a.channel member Alltlxand rails 39 and 41 and similar to members 29, 30 ,and 35V so that they not only realign the links but tighten the ,c hain. The rails 39 can Abe aiiixed tothe respective bedplates inany suitable manner, -e,.g.,fby welding, screws, bolts, etc., and rails 41 can be made v adjustablelike members 28 by means of lead screws, etc. .While a spacehasheen shown between the end of members 39 and 40 ofunit 3811116. .minimumpitch sprocketv-,Zti-.for-,the -sake of clarity, in actual construction members 39 and 40Y can be extended soas to form. a guiding surface-right vup tothe point The other arm of the L-shaped bracket is where the link pins contact with the sprocket teeth. Similarly, members 29 and 30 of unit 13 can be extended to the point where the link pins contact with the sprocket teeth of driving sprocket 19. Thus the upper portions of the guide members may overlap the flat surfaces of the sprockets. A curved cam 42 is provided about each sprocket to open the grippers and allow them to close and grip the web W as it passes into the path of the grippers.

In Fig. 2 the links 18 are stackedpairs thus providing a relatively smooth surface to engage with the horizontal surfaces of the track in the stretching unit. The contour of the links can be modified so that they can be stacked in units of 3 or 4 or even more. Further, it is not necessary that each pin be connected to the adjacent links through the pivot hole of one and the elongated slot of the next link. Thus, in Figs. 6 and 7, a four-link stacking arrangement is shown where alternate pairs are spaced. They are shown in solid elevation for clarity.

Fig. 8 illustrates a three-link stacking Varrangenientr in section and is self-explanatory.

Figs. 9, l0, 1l, and l2 require no extended description since their function is clear from the above. It will be noted, however, that the angle 0 remains the same regardless ofthe amount the link has rotated and the chain thereby extended. The force tending to rotate the link therefore will remain constant. in Fig. S the angle 0 increases with the rotation of the link as does the rotating force.

Figs. 1l and 12 merely illustrate that the chain links can be reversed and still function the same when the chain travels in the same direction. As stated above the chain may travel in either direction.

In Figs. 13 and 14 there is illustrated a series of grippers mounted on successive pins 18. The plates of these grippers have been eliminated for the sake of clarity. The chain links have not been shown for a similar reason. However, the assembly on a pin is shown in Figs. 2 and 3.

In placel of the pivoted arms 23 which have arounded bottom there may be substituted pivotcd arms with an elongated iiat plate which is provided with pins topierce the web to be stretched. This type of gripper isillustrated in U.S. Patent 650,385 to Gadd.

While the sprocket of minimum pitch has been f, described as a driven sprocket it may be connected by a. suitable chain or series of gears to the same `source of power that turns the driving sprocket ofrnaximumpitch.

The contour of the links can vary considerablyM-so long as there is a pivot point and a slot which allow the pins to separate. Thus, in the alternate ,form of construction shown in Fig. 5, the pivotkhole and adjacent end of the slanting slot are near the heel of the L-shaped link and the pivot hole is nearest the base. .Obviously, still other congurations can be used. The links need not be L-shaped but may be oval, etc., preferably with cut-away portions if necessary so that the links may close to minimum pitch and expand tomaximum pitch without interference with the pins.

Various heating and cooling devices, e.g.l amps,lcoils, jackets, etc., can be provided along theweb travel to control the operations. Thus, the grippers can be heated or cooled. Various other types of grippers can be substituted for those shown and described above.

The operation of the apparatus will now be explained with reference to the stretching of a non-oriented superpolymer film, eg., polyethylene terephthalate films of the type described in Whineld et al., U.S. Patent 2,465,319. A web W of non-oriented or non-stretched polyethylene terephthalate tilm free from a thin coating or coated with a vinylidene chloride copolymer layer of the kind described in Alles and Sane, U.S. app. Ser. No. 151,274, tiled March 27, 1950, now U.S. Patent 2,627,088, and in Pitzel U.S. Patent 2,570,478 is fed directly from an extrusion device or from a supplyv roll (noneA being In the link shownv shown) into the stretching apparatus. The lower surfaces of the respective edges of the web are directed onto gripper base plates 27 and gripper arms fall by gravity into contact with the upper surface of the web. As the web passes through the stretching device to a windup station or other apparatus (not shown) tension is gradually applied laterally and longitudinally because of the divergency of the bedplates and because the links are actuated and pivot so that the pitch (i.e., distance between successive pins 18) increases from minimum to a greater pitch determined by the amount of stretching it is desired to effect in the web. The grippers are released after the maximum desired stretch has been accomplished. The web then passes on for any desired further treatment.

Instead of relying upon gravity to actuate the gripper arms they may be actuated by a cam surface or tripping device similar to that described above for releasing the gripper arms but in reverse direction.

It should be apparent to Athose skilled in the art that the invention is not limited to the stretching of polyethylene terephthalate film but may be used in stretching webs of many diverse types including not only resins and superpolymers, e.g., nylon, polyethylene, polyvinyl chloride, poly(vinyl chloride co vinyl acetate); cellulose derivatives, eg., cellulose acetate, cellulose formate, cellulose propionate, cellulose acetate-butyrate; methyl, ethyl, butyl, benzyl, allyl and crotyl celluloses; rubber hydrochloride, polystyrene, but also fabrics made of wool, silk, cotton, cellulose acetate, viscose rayon, nylon, etc. Metal foils, e.g., lead, aluminum, etc., can be stretched in a similar manner.

The apparatus is not limited to stretching so that a permanent set is obtained as it may be used to make elastic fabrics by suitable techniques along the selvage, etc., during travel of the web. It is useful for controlled shrinking of fabrics in which case it would be operated in reverse.

While the apparatus is primarily designed for stretch-A ing in two directions, it is not limited to that treatment. Thus, by adjusting the bedplates so that the path of the pins is parallel to the sides of the web, longitudinal stretching only can be accomplished.

As many widely different embodiments of this invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited except as defined by the claims.

This case is a divisional application based on Miller application Serial No. 278,252, filed March 24, 1952, now U.S. Patent No. 2,755,533.

What is claimed is:

1. A link for a variable pitch chain, said link comprising an L-shaped plate having a leg portion and a lateral foot portion, the two surfaces of the plate being flat in a single plane, said foot portion having a pivot hole and an elongated slot, said slot and said hole extending through said plate in a perpendicular direction, the perpendicular axis of one of said ends being closer to the perpendicular axis of the said pivot hole than any other point on the locus of the longitudinal center line of the said slot; said hole and slot being adapted to receive adjacent pivot pins which are disposed perpendicular to said surfaces and intert with the holes and slots when a plurality of such links are placed in overlapping relationship so that the pivot pins extend through the pivot hole of one link and the slot of an adjacent link in forming a variable pitch chain; the upper outside edge of the leg portion being curved inwardly to form a camming surface which is adapted tov coact with a guiding surface.

2. A link fo'r a variable pitch chain, said link comprising an L-shaped plate having a leg portion and a lateral foot portion, the two surfaces of the plate being flat in a single plane, said foot portion having a pivot hole and an elongated slot of uniform width having semicircular ends, said slot and said hole extending through said plate in a perpendicular direction, the perendicular axis of one of said ends being closer to the perpendicular axis of the said pivot hole than any other point on the locus of the longitudinal center line of the said slot; said ho'le and slot being adapted to receive adjacent pivot pins which are disposed perpendicular to said surfaces and interlit with the holes and slots when a plurality of such links are placed in overlapping relationship so that the pivot pins extend through the pivot hole of one link and the slot of an adjacent link in forming a variable pitch chain; the upper o'utside edge of the leg portion being curved inwardly to form a camming surface which is adapted to coact with a guiding surface. 4

3. A link as defined in claim 2 wherein said slot is straight.

4. A link as defined in claim -2 wherein said slot is curved.

5. A link as defined in claim 2 wherein said slo't extends in a direction between the heel and toe of the foot portion and is between the hole and the camming surface.

6. A link as defined in claim 2 wherein said slot extends in a direction between the heel and toe of the foot portion and the hole is between the slot and the camming surface.

7. A variable pitch chain comprising at least four chain links as set forth in claim 1, the links on each side of the chain being located and positioned with respect to each other in overlapping relationship such that the pin connecting the pivot holes of one pair of links extends through the slots of an adjacent pair of links, whereby, upon camming action being exerted on said camming surface, rotation of a link about the pin in its hole fo'rces the pin of the next adjacent link along its slot, effecting the linear displacement of adjacent links in said variable pitch chain.

References Cited in the Ele of this patent UNITED STATES PATENTS 675,866 Weichelt et al June 4, 1901 1,840,486 Butterworth Ian. 12, 1932 1,984,377 Krug Dec. 18, 1934 2,285,820 Macknight June 9, 1942 

